The present invention relates generally to modular integrated accessory mounting assemblies for combat weapons. More specifically, the present invention relates to an accessory mounting assembly, which includes an actuator that provides adjustable spring tension to control the clamping force exerted by the actuator against the firearm interface rail, and which provides added tensile strength for the threaded governor post.
As the field of combat and commercial weaponry expands, numerous add-on enhancements have become available for attachment to standard firearms, thereby upgrading the capability of the firearm. Of particular interest in the area of combat weapons is the well-known M16/M4 weapon system (M16 and M4 are trademarks of Colt Defense, Inc.) and the civilian AR15 platform. Generally, the M16/M4/AR15 weapon 2, as depicted in FIG. 1, includes a lower receiver 4, upper receiver 6, butt stock 8, and barrel 10.
The newer models of the M16/M4/AR15 weapons include a mil-std 1913 dovetail rail 12 extending along the top of the upper receiver. This integrated receiver rail 12 provides a mounting point for many types of enhancement devices such as iron sights, optical scopes, laser sights and other sighting devices. However, space on the upper receiver rail 12 is limited, and users often have multiple sighting devices that are each tailored to perform in different situations.
Responding to this need, the applicant has developed a modular integrated rail system (A.R.M.S.® S.I.R.® system) shown at FIG. 2, and fully described in U.S. Pat. No. 6,490,822, the entire contents of which are incorporated herein by reference. These modular integrated rail systems generally include an upper hand guard 14, a means 16 for securing the upper hand guard 14 to the weapon 2, a lower firearm accessory 18 (in most cases this is a lower hand guard), various optional rail segments, and in many cases, a sling swivel 20 for attaching a shoulder sling to carry the weapon 2.
An interface means 16 is provided at the rearward end of the upper hand guard 14 to removably secure the upper hand guard 14 to the firearm 2. In the original S.I.R. system as shown in U.S. Pat. No. 6,490,822, the interface includes elongated sleeve that secures the upper hand guard 14 to the dovetail rail 12 on the top of the upper receiver 6 of the weapon 2 as well as a U-shaped yoke or clamp (not shown) that secured the upper hand guard 14 to the barrel nut of the weapon. In the other S.I.R. systems, the interface means 16 is a larger U-shaped yoke or clamp that secures the upper hand guard 14 exclusively to the barrel nut with the upper rail 22 sitting flush with the receiver rail 12.
As is well known in this area, field modification of weapon configurations is critical in combat situations. In this regard, standardized attachment assemblies have been developed to allow quick and easy removal and mounting of these devices relative to the dovetail rails.
Such an attachment device is disclosed in U.S. Pat. No. 5,276,988, issued on Jan. 11, 1994 to the present applicant, the contents of the '988 patent being incorporated herein by reference. Generally, the prior art attachment assemblies as shown at FIGS. 3 and 4 include a main body 24 having a lower portion that is configured to engage the dovetail rail 22 on the upper receiver or handguard and an upper portion 26 that can take on a variety of configurations depending on the accessory that is to be mounted thereon. The lower portion of the mounting assembly has a first engagement member 28 extending downwardly along one side thereof for engaging one side of the dovetail rail 22. Further, a boss formation 30 is provided adjacent the side of the main body to receive a clamping assembly 32 that is particularly suited to be releasably engaged with a second side of the dovetail rail 22 such that the clamping assembly cooperates with the first engagement member 28 to retain the modular mounting assembly in its installed position on the dovetail rail. The clamping assembly 32 generally includes a foot portion 32A with a cam surface 32B to engage the angulated surface of the dovetail rail 22, a post (not shown) extending upwardly through the boss formation 30 and a head portion 32C secured to the top end of the post and having actuator arm 32D to facilitate rotation of the foot portion 32A. The clamping assembly 32 further includes spring washers (not shown), which are captured between the bottom surface of the head portion 32C and the boss 30 (or a bushing within the boss) to provide a self-adjusting amount of spring tension as the clamping assembly 32 is rotated into engagement with the rail 22. These springs generally allow a limited, self-adjusted amount of biased vertical movement of the clamping foot 32A relative to the boss and the rail 22. Because the head portion 32C of the clamping assembly 32 is secured in a fixed position on the top end of the post, the spring are compressed by a fixed amount and therefore the force exerted by the foot 32A on the rail 22 was generally variable, but variable only within a certain range as determined by the initial spring tension. This small range of self-adjustment is critical in being able to accommodate the small dimensional variations allowed mil-std 1913 rail configuration.
As the commercial AR-15 marketplace increased over the last 15 years, many commercial manufacturers loosened their tolerances for the mil-std 1913 dovetail dimensions resulting in dovetail rails that do not meet the mil-std 1913 specifications and which are both larger and smaller than the mil-std 1913 dimensions. These small changes in tolerance meant that the fixed spring variance in the earlier versions of the mounting assemblies often did not fit correctly onto the non-mil-std 1913 dimensioned rails.
Accordingly, in the commercial market there is a need to adjust the range of the spring tension. However, making this adjustment available to the end user often leads to overtightening and physical damage to both the rails and the mounting assemblies. Overtight is not better in these circumstances.
Accordingly, there is a need for a modular mounting assembly that includes an ability to adjust the spring tension that is exerted by the clamping foot while also providing superior strength and reliability in the field.